This is the ONLY book Dell ever put in a
jacket. The oddity here is not necessarily the dust jacket, but the reason WHY.
The answer is: nobody is really sure.

The cover art on the book is by Walter
Brooks. The dust jacket is by Griffith Foxley. William H. Lyles, the Dell
bibliographer, indicates there might have been a little friction between Brooks,
who was art director at Dell at the time, and the Sales department. Evidently,
Sales considered the original cover "too provocative," and thought it needed to
be covered up. It's hard to imagine that ANYONE would think it more provocative
than the resultant dust jacket. Only one reprint was jacketed. The dj's are
extremely scarce today.